Following her debut performance of the track at the Grammy Awards last month, it was thought the song referenced Perry's split from Russell, as it includes the lyrics: "You can keep the diamond ring, it don't mean nothing anyway/ In fact, you can keep everything — except for me."
However, the 27-year old has now revealed that she penned the tune long before her divorce from Brand, telling Access Hollywood: "I wrote Part of Me two years ago and I always knew that Part of Me was a special song.
"It feels like my life plays out with these songs. I feel like I'm in some kind of weird Truman Show where I'm like, 'Why is this single appropriate now and it wouldn't have been appropriate then?' It's just so crazy."
She added: "I guess the universe is kind of - we're kind of like, dancing together in some weird way. Does that make sense or am I being too hippie?"
While Katy has sworn Part Of Me is not about Russell, the funnyman has apparently vowed to never get married again, with a friend of Brand's telling the Daily Star: "Russ was devastated when things with Katy went wrong.
"We were all worried he’d go off the rails again. He managed to pull himself together and he’s fine now. He’s had a chance to look back and assess everything and reckons marriage isn’t for him. Russ was never too keen on it in the first place but loved Katy and thought it’d work.”
As for his rumoured romance with Mexican artist Oriela Medellin Amieiro, the source added: "He doesn’t want to string her along, but he’s dead set on not getting married again."
Watch MTV News on the hour every hour on MTV - Sky Channel 126 and Virgin Channel 134